Diazo sensitizing formulations containing a xanthine and an imidazoledione



United States Patent 3,386,828 DIAZG SENSITIZING FORMULATIONS CONTAINING A XANTHINE AND AN IMIDAZOLEDIONE Chester E. -Slim0wicz, Vestal, N.Y., assignor to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 19, 1965, Ser. No. 498,110 13 Claims. (Cl. 96-91) The present invention relates in general to the production of light-sensitive diazotype photoprinting materials and more particularly to sensitizing compositions useful in preparing same.

As is well known, the manufacture of light-sensitive diazotype materials involves the application to a suitable base of a sensitizing solution comprising one or ore stabilized light-sensitive diazonium compounds. The latter are characterized in that upon exposure to actinic radiation they undergo a photolytically induced decomposition being thus rendered incapable of coupling with an azo dye coupling component. In the processing of such materials they are exposed to light under a pattern, e.g., photographic transparency, line drawing or the like, whereby the light-sensitive diazonium compound is decomposed imagewise in accordance with the light transmitted by the pattern. In the case of two-component diazotype materials, i.e., where one or more coupling components as well as suitable stabilizers against precoupling are incorporated into the sensitizing composition, a positive dye image is formed by subjecting the element thus exposed to an alkaline environment, preferably an ammonia atmosphere, to initiate the coupling reaction by the undecomposed diazonium and coupler.

Two-compartment diazotype materials are in general preferred since the requirement for the use of an aqueous, coupler-containing developer composition is obviated. This, of course, presents several processing advantages including, for example, the elimination of the manifold problems associated with loss of sensitizing component, stabilizer, etc.,'via diffusion into the aqueous de veloper solution. Accordingly, the two-component process makes possible the obtension of reproductions characterized by superior dye density, brightness, image quality and the like.

It is of utmost importance to the effectiveness of twocomponent diazotype processing that the light-sensitive composition be adequately stabilized against pre coupling and correspondingly, that uniform, homogeneous dispersion of the involved ingredients be achieved. Accordingly, considerable industrial activity has centered around the research and development of compounds which, when incorporated into diazo sensitizing composi tions provide the aforenoted results. As will be readily apparent, the occurrence of precoupling in the sensitized composition will, as a practical matter, vitiate any attempt to obtain an image reproduction having acceptable photographic qualities.

Oonventionally, two-component diazo sensitizing solutions are prepared in an aqueous media maintained under an acid pH. However, a considerable number of the coupling components conventionally employed exhibit a somewhat limited solubility in the aqueous sensitizing media with the consequence that the range of selection of available coupling components is correspondingly circumscribed. The problem of limited water solubility has likewise been encountered in connection with the lightsensitive diazo compound as well, and particularly the paraaminobenzene diazonium salts which contain oleophilic substituents such as alkyl. The use of difiicultly soluble coupler and/or diazo compounds tends to militate against any attempt to provide such compositions, when coated upon the substrate material, in a homogeneously dispersed form, the latter result being, of course, of paramount importance if an image reproduction of satisfactory photographic quality is to be obtained. The consequences attending the failure to achieve the requisite uniform dispersion of components are for the most part self-evident. However stated, the net effeet is invariably faulty image reproduction with serious impairment of image density, contrast and the like.

The foregoing problems are found to be particularly manifest in connection with the use of diflicultly soluble coupling components of the hy-droxy naphthalene series. Typically, compounds of the latter type exhibit an appreciable order of insolubility in acidified aqueous media and especially within the pH range normally extant in diazo sensitizing compositions. Moreover, many of the n-aphthol couplers contain further su-bstituents which aggravate the insolubility problem, e.g., amide, amine, etc., which in turn can be substituted by further insolubilizing groups such as alkyl, aryl and the like.

In an attempt to overcome or otherwise alleviate the foregoing and related problems, the art has resorted to the practice of providing two-component diazo sensitizing compositions with various solubilizing addenda for purposes of increasing the solubility of the coupler and/or diazo compounds in the acid diazo sensitizing medium. Particularly beneficial results have been obtained heretof'ore by the utilization of solubilizing agents which are compounds of the xanthine family. As examples of the latter mentioned compounds which have achieved a significant measure of commercial acceptance there may be mentioned caffeine, theophylline, theo'bromine and the like. Purportedly, xanthine compounds of the aforementioned type function not only to abate considerably the above described solubility problems, but in addition, in many instances function as stabilizers, i.e., enhance the keeping quality of the two-component diazotype materials probably by retardation of premature coupling.

In accordance with the discovery forming the basis of the present invention it has been ascertained that the solubilizing and stabilizing effects made possible by the use of xanthine compounds can be synergistically enhanced by employing in combination therewith one 01 more compounds of the im-idazoledione family.

Thus, a primary object of the present invention resides in the provision of solubilizing synergists for twocomponent diazo sensitizing compositions wherein the problems associated with difiicultly soluble diazo and/or coupling components are eliminated or at least mitigated to a substantial extent.

Another object of the present invention resides in the provision of diazo sensitizing compositions characterized by outstanding capacity to yield photographic images having improved image dye density, brightness, contrast and the like.

A further object of the present invention resides in the .provision of diazotype photoprinting elements having exceptional resistance to pre coupl-ing.

The attainment of the foregoing and related objects is made possible in accordance with the present invention which, in its broader aspects, includes the provision of two-component diazo sensitizing compositions containing as essential ingredients (1) a xanthine compound and (2) imidazoledione compound of the following structural formula:

wherein R R R and R are independently selected from the group consisting of hydrogen, lower alkyl of 1-4 carbon atoms, e.g., methyl, ethyl, propyl, isobutyl, etc., aryl, e.g., phenyl, naphthyl, etc., aralkyl, e.g., benzyl, alkaryl, e.g., tolyl, xylyl, etc, and cycloalkyl, e.g., cyclohexyl, cyclopentyl, etc., and the like; the foregoing groups may, of course, contain further substituents the nature of which is not particularly critical with the obvious qualification that the coupling reaction mechanism be not adversely aifected. Thus, the compounds included by the above formula should be devoid of such groups as NO NH and SO H.

Two-component diazo sensitizing compositions modified in accordance with the present invention are found to be characterized not only by a mere uniform dispersion of the involved ingredients but in addition by a marked increase in resistance to pre-coupling. A particularly surprising discovery relates to the fact that the above described combination of solubilizing synergists can be employed in any two-component diazo sensitizing composition, i.e., regardless of the solubility of the diazo coupler, stabilizer, etc., whereby there is provided a more compatible sensitizer media having exceptional stability even under high humidity storage conditions. As will be realized, however, the solubility-promoting effects are particularly beneficial in connection with two-component diazo sensitizing compositions containing one or more difficulty soluble coupling and/ or diazo components.

As examples of compounds encompassed by the above formula and found to be particularly suitable to the purposes of the present invention there may be mentioned the following:

Hydantoin 5,5-dimethyl hydantoin l-ethyl hydantoin 1,5-dimethyl hydantoin, etc.

The above compounds may be added to the sensitizing medium in a wide range of proportions so long as sufficient amounts be present to impart the desired degree of solubilization. However, in general, it is found that optimum realization of improvements provided herein is obtained when utilizing the imidazoledione compound in amounts ranging from about 0.5% to about 3.0% and preferably from about 1% to about 2% by weight based on the total weight of sensitizing solution. Within the aforestated range, the proportions selected will be infiuenced, of course, by a number of factors in addition to the solubility of the coupling component. For example, the water solubility of the remaining components, e.g., diazo compound, stabilizer, etc., will likewise be a factor as will the relative concentrations of each of such ingredients. In any event, optimum concentrations in a particular circumstance can be readily ascertained by routine laboratory experimentation. It will be understood, of course, that mixtures of two or more of the imidazoledione compounds may likewise be employed to advantage.

The compounds of the above formula are well known in the art, their preparation being described in standard reference works. In general, such compounds can be formed by the action of acid chlorides or anhydrides upon urea or by the action of phosphorus oxychloride upon the salts of urea with organic acids followed by hydrolysis of the resultant product to yield the imidazoledione derivative. For example, hydantoin can be prepared by simple hydrolysis of glycollic acid; l-methyl-lhydantoin can be prepared by the partial hydrolysis of ereatinine.

The xanthine compounds found to be eminently suitable for use in the present invention include, for example, caffeine, theophylline, theobromine, and the like; caffeine is particularly preferred since it appears to possess a relatively high activity, i.e., solubilizing potential. As with the imidazoledione compound, the concentration of the xanthine is critical solely from the standpoint of its being present in amounts sufficient to impart the desired degree of solubilization, etc. In general, it is found that the foregoing results can be obtained by employing the xanthine compound in amounts ranging from about 0.5% to about 2.5% by Weight based on the total weight of sensitizing solution with a range of from about 1% to about 2% being preferred.

The xanthine and imidazoledione components may be preliminarily provided in the form of a compatible solution or conversely, may be added separately to the diazo sensitizing composition.

In formulating the sensitizing compositions of the present invention any combination of diazo and coupling component may be employed which is suitable for the preparation of two-component diazotype layers, i.e., dry development papers which upon development yield the shade desired for the final image. Diazo compounds which are suitable for such two-component materials are known to be those which are derived from 1,2- and 2,1- aninonaphthols, 1,4-aminonaphthols and aromatic p-diamines of the benzene series, particularly p-phenylene diamines which are monoor disubstituted on one of the two amino groups. As examples of such diazo compounds which are commonly used in the production of diazotype images, there may be mentioned the diazo derivatives of the following compounds:

4-amino-N-methylaniline 4-amino-N-ethylaniline 4-aminodiphenylamine 4-amino-N-(hydroxyethyl) aniline 4-amino-N-(2,5-dibromobenzyl) aniline 4-amino-N,N-dimethylaniline 4-amino-N,N-diethylaniline 4-amino-N,N-dipropylaniline 4-amino-N-methyl-N-(ti-hydroxyethyl) aniline 4-amino-N- B-hydroxyethyl) aniline 4-amino-N-butyl-N-(,B-hydroxyethyl) aniline 4-amino-N,N-di ;8-hydroxyethyl) aniline 4-amino-N-benzyl-N-ethylaniline 4-amino-N-ethyl-3-methylaniline 4-amino-N,N-dimethyl-3-methylaniline 4-amino-N,N-dimethyI-Z-methylaniline 4-amino-N,N-diethyl-3-methylaniline 4-amino-N-ethyl-N- B-hydroxyethyl) 3-methylaniline 4-amino-N-cyclohexyl-2-methoxyaniline 4-amino-N,N-di (fl-hydroxyethyl) 3-methoxyaniline 4-amino-N,N-diethylamino-3-ethoxyani1ine 4-amino-N-benzyl-2,S-diethoxyaniline 4-amino-3-chloro-N,N-di(,B-hydroxyethyl) aniline 4-amin0-3-carboxy-N,N-diethylaniline 1-amino-2-hydroxynaphthalene-4-sulfonic acid Z-amino-l-hydroxynaphthalene-5-sulfonic acid 2-amino-1-hydroxynaphthalene-3,6-disulfonic acid 3-aminocarbazol, and the like.

The diazo derivatives of the above mentioned compounds may be employed in the form of their stabilized salts, as exemplified by p-diphenylamine diazonium sulfate or in the form of zinc chloride or boron trifluoride double salts, etc. As examples of such stabilized double salts, there may be mentioned the zinc chloride or boron trifiuoride double salts of:

p-Diethylaminobenzenediazonium chloride p-Di S-hydroxyethyl) amino-Z-methylb enzenediazonium chloride p-Ethyl-(fi-hydroxyethyl) aminobenzenediazonium chloride p-Diethylamino-3-ethoxylbenzenediazonium chloride and the like.

Moreover, the diazo compound may be employed in the form of the anhydride as exemplified by:

2-amino-l-hydroxynaphthalene-4-sulfodiazonium anhydride 2-amino-1-hydroxynaphthalene-S-sulfodiazonium anhydride 1-amino-2-hydroxynaphtha1ene-4-sulfodiazonium anhydride 1-amino-2-hydroxynaphthalene-5-sulfodiazoninum anhydride and their water soluble alkali metal salts.

Any of the usual azo coupling components may be employed for use herein, particular examples thereof including without limitation the following:

Resorcinol- Phloroglucinol 3-hydroxyphenylurea 3-(N-3-aminobenzoyl) aminophenol 3-(N-4-aminobenzoyl) aminophenol 2,3-dihydroxynaphthalene 2,7-dihydroxynaphthalene 2,3-dihydroxynaphthalene-6-sulfonic acid 1-hydroxynaph-thalene-4-sulfonic acid 2-hydroxynaphthalene-3,6-disulfonic acid 1-hydnoxynaphthalene-3,8-disu1fonic acid 2-amino-8-hydroxynaphthalene-3,6-disulfonic acid 2,3-dihydroxynaphthalene-G-carboxylic acid 1-amino-7-hydroxynaphthalene 1-amino-8-hy=droxynaphthalene-3,6-disulfonic acid 4-hydroxybenzimidazole hydrochloride 2-hydroxy-7,-8-naphthimidazole hydrochloride S-hydroxy-1,2-naphthimidazole hydrochloride 7-hydroxy-1,2-naphthimidazole hydrochloride 2-hydroxynaphthalene-8'biguanide 7-hydroxynaphthalene-2-bigu-anide 7-hydroxynaph-thalene-1 biguanide S-hydroxynaphthalene-l biguanide 2,2,4,4'-tetrahy-droxydiphenyl 3,3',5,5'-tetrahydroxybiphenyl 4-hydroxyquinolone 1-methyl-4-hydroxyquinolone (2) 1-(2'-methoxyphenyl)-4-hydroxyquinolone (2) 1-phenyl-3-methy1pyraz0lone 1- 4'-sulfophenyl) -3-m ethyl pyrazolone 1-tolyl-3 methylpyrazolone Acetoacetanilide Acetoacet-o-toluidide Acetoacetic acid benzyla'mide, and the like.

In addition to the foregoing ingredients, the sensitizing composition may also contain the various adjuncts conventionally employed in the manufacture of light-sensitize diazotype materials including hygroscopic agents, e.g., propylene glycol, one of more acid materials, e.g., citric acid, tartaric acid, tricarballylic acid, phosphoric acid and the like; suitable stabli-lizing or anti-oxidizing agents such as thiourea, allyl, isothiocyanate and the like which function to retard background discoloration on the finished print. Metal salts for intensification of the dyestulf image may also be added including zinc chloride, ammonium sulfate, nickel sulfate and the like. Suitable wetting agents include without limitation, saponin, lauryl sulfonate, keryl benzene sulfonate, the oleic acid amide of N-methyl taurinc and the like.

The composition thus formulated may be applied to any suitable base material including paper, metal, as well as materials derived from film-forming synthetic resins, e.g., polyethylene terephthalate. Other suitable base materials include cellulose acetate, cellulose acetate butyrate and the like; textiles including fabrics derived from cotton, cellulose acetate, batiste, regenerated cellulose of the xanthate or viscose type, balloon cloth, knitted rayon jersey, mixed cotton and rayon or other absorbent fabrics, and woven or felted materials which can be impregnated with the diazo solution.

The following examples are given for purposes of illustrating the presentinvention and are not to be regarded in any way as being limitative thereof.

Example I A two-component diazo sensitizing composition is prepared consisting of:

The above solution is coated on a paper base and exposed to actinic light under a density step wedge and developed with ammonia vapors in a commercial model of an ammonia developing machine. The print obtained shows .a considerable enhancement in dye density and brightness When compared to prints made on paper similarly treated with the above coating solution but containing no caffeine and hydantoin.

Example II High grade-sulfite bond paper is coated with a sensitizing solution of the following com-position:

Ethylene glycol mls 5.0 Isopropanol mls 1.0 Citric acid gms 4.0 C-afieine gms 2.0 Thiourea gms 5.0 2,3dihydroxynaphthalene-6-sulf0nic acid gms 4.0

Zinc chloride double salt of p diethylaminobenzenediazonium chloride gms 1.6 Saponin gms 0.1 Zinc chloride gms 4.5 Magnesium chloride (anhydrous) gms 1.5 Hydantoin gms 1.5 Water to make mls.

Prints and comparisons made in a manner analogous to those described in Example I reveal the same improvements regarding image reproduction quality.

Example III A diazotype paper stock made of rag paper is coated with an aqueous solution having the following composition:

l-methyl-4-oxyquinolone-(2) gms 13.0 Zinc chloride double salt of p-dlethylaminobenzenediazonium chloride gms 22.0 Ethyl alcohol mls 50.0 Citric acid J. gms 80.0 Hydantoin gms 5.0 Thiourea gms 40.0 Zinc chloride gms 39.0 Caffeine gms 15.0

Water to make 1 liter.

Comparison of prints produced in the manner described in Example I reveals like improvement in image reproduction quality.

Example IV An aqueous solution of the following composition is prepared and applied to a starch-sized cotton cloth:

Gms. Zinc chloride double salt of p-diethyl-amino-2- me'thylbenzenediazoninm chloride 5.0 2,3-dihydroxynaphthalene 8.0 Citric acid 50.0 Hydan-toin 10.0 Zinc chloride 45.0 Saponin 0.1 Caffeine 10.0

Water to made 1 liter.

An improvement similar to that described in the above examples with regard to image-dye density, brightness, visual contrast and the like is obtained.

Example V A solution having the following composition is prepared and coated on a diazotype paper stock made of rag paper:

Resorcinol gms 25.0 Zinc chloride double salt of N-methyl-N-(B-hydroxyethyl) aminobenzenediazonium chloride gms 5 0.0

Water to make 1 liter.

Prints and comparisons made in a fashion analogous to those in Example I reveal similar improvements in image reproduction quality in connection with the sample sensitized with the composition including the hydantoin and caffeine components.

Example VI A coating solution having the following composition is coated on diazo stock paper:

Glycerin 1nls 50.0 Citric acid gms v 50.0 Caffeine ..grns 8.0 Thiourea gms 50.0 Acetoacetanilide gms 0.8 2,3-dihydroxynaphthalene gms 1.0

2,3-dihydroxynaphthalene-6-sulfonic acid gms 40.0 Zinc chloride double salt of p-dimethyl-aminobenzenediazonium chloride gms 25.0 Saponin gms 0.5 Zinc chloride gms 30.0 Hydantoin gms 25.0

Water to make 1 liter.

As with the above examples the prints and comparisons clearly indicate a significant improvement as regards image dye density, brightness, visual contrast and the like.

Example V II Example I is repeated except that the caffeine is replaced by theobromine in the same amount. The print obtained upon exposure and development reveals similar improvement when compared to the control sample.

Example VIII Example I is repeated except that the hydantoin is replaced by 1,5-dimethylhydantoin. The prints obtained indicate a like improvement in image reproduction quality.

Improvements similar to those described in the above examples are obtained when utilizing any of the coupling and/or diazo compounds more fully enumerated hereinbefore. Furthermore, such improvement is in no way affected by the nature of the base material employed and thus, the use in this connection of film-forming plastic materials, e.g., polyethylene terephthalate cellulose esters, regenerated cellulose, is found to be eminently suitable. Moreover, the base material, may, if desired, be provided with one or more suitable precoats, e.g., synthetic resin, in the manner well known in the diazotype art.

While there are disclosed above a number of embodiments of the invention'herein described, it is obvious that various changes may be made without departing from the nature and spirit of the invention. Therefore, the invention is not limited to the specific details herein described except as defined in the appended claims.

What is claimed is:

1. A two-component light-sensitive diazo composition comprising a compatible aqueous solution of a lightsensitive diazo compound and a coupling component, said solution further containing as essential ingredients (a) a xanthine compound and (b) an imidazoledione compound of the formula:

iii.

wherein R R R and R are independently selected from the group consisting of hydrogen, lower alkyl, aryl, aralkyl, alkaryl, and cycloalkyl.

2. A composition according to claim 1 wherein said imidazoledione compound comprises hyd'antoin.

3. A composition according to claim 1 wherein said imidazoledione compound comprises 1,5-dimethylhydantoin.

4. A composition according to claim 1 wherein said xanthine compound comprises caffeine.

5. A composition according to claim 1 wherein said xanthine compound comprises theobromine.

6. A two-component light-sensitive diazo composition comprising a compatible aqueous solution of a light-sensitive diazo compound, a diflicu-ltly soluble coupling component, said solution containing as essential ingredients (a) from about 0.5% to about 2.5% by weight based upon the total weight of sensitizing solution of a xanthine compound and (b) from about 0.5% to about 3.0% by weight based upon the total weight of sensitizing solution of an imidazoledione compound of the formula:

tilt.

wherein R R R and R are independently selected from the group consisting of hydrogen, lower alkyl, aryl, aralkyl, alkaryl, and cycloalkyl.

7. A composition according to claim 6 wherein said imidazoledione compound comprises hyd antoin.

8. A composition according to claim 6 wherein said imidazoledione compound comprises 1,5-dimethylhydantoin.

9. A composition according to claim 6 wherein said xanthine compound comprises caffeine.

10. A composition according to claim 6 wherein said xanthine compound comprises theobromiue.

9 10 11. A diazotype photoprinting material comprising a References Cited daiml p e p 7 2,270,756 1/11942 Kern 96--911XR 12. A di-azotype ph'otoprinting material according to 5 $419,296 5010mm 96-91XR claim 11 wherein said base comprises paper. 2,617,726 2" Kessels 3 9675 '13. A diazo [ype photoprinting element according to 3,248,220 4/1966 Van Rhlln 96-49 XR claim 11 wherein said x-anthine compound comprises caffeine and said imidazoledione compound comprises hy- NORMAN TORCHIN Primary Examiner dantoin. C. L. BOWERS, Assistant Examiner. 

1. A TWO-COMPONENT LIGHJT-SENSITIVE DIAZO COMPOSITION COMPRISING A COMPATIBLE AQUEOUS SOLUTION OF A LIGHTSENSITIVE DIAZO COMPOUND AND A COUPLING COMPONENT, SAID SOLUTION FURTHER CONTAINING AS ESSENTIAL INGREDIENTS (A) A XANTHINE COMPOUND AND (B) AN IMIDAZOLEDIONE COMPOUND OF THE FORMULA: 